A conserved NR5A1-responsive enhancer regulates SRY in testis-determination

The Y-linked SRY gene initiates mammalian testis-determination. However, how the expression of SRY is regulated remains elusive. Here, we demonstrate that a conserved steroidogenic factor-1 (SF-1)/NR5A1 binding enhancer is required for appropriate SRY expression to initiate testis-determination in humans. Comparative sequence analysis of SRY 5' regions in mammals identified an evolutionary conserved SF-1/NR5A1-binding motif within a 250 bp region of open chromatin located 5 kilobases upstream of the SRY transcription start site. Genomic analysis of 46,XY individuals with disrupted testis-determination, including a large multigenerational family, identified unique single-base substitutions of highly conserved residues within the SF-1/NR5A1-binding element. In silico modelling and in vitro assays demonstrate the enhancer properties of the NR5A1 motif. Deletion of this hemizygous element by genome-editing, in a novel in vitro cellular model recapitulating human Sertoli cell formation, resulted in a significant reduction in expression of SRY. Therefore, human NR5A1 acts as a regulatory switch between testis and ovary development by upregulating SRY expression, a role that may predate the eutherian radiation. We show that disruption of an enhancer can phenocopy variants in the coding regions of SRY that cause human testis dysgenesis. Since disease causing variants in enhancers are currently rare, the regulation of gene expression in testis-determination offers a paradigm to define enhancer activity in a key developmental process.

A mesomelic skeletal dysplasia, Kantaputra-like, not related to HOXD cluster region, and with phenotypic gender differences

Mesomelic skeletal dysplasia is a heterogeneous group of skeletal disorders that has grown since the molecular basis of these conditions is in the process of research and discovery. Here, we report a Brazilian family with eight affected members over three generations with a phenotype similar to mesomelic Kantaputra dysplasia. This family presents marked shortening of the upper limbs with hypotrophy of the lower limbs and clubfeet without synostosis. Array-based CNV analysis and exome sequencing of four family members failed to show any region or gene candidate. Interestingly, males were more severely affected than females in this family, suggesting that gender differences could play a role in the phenotypic expressivity of this condition.

NR5A1-related 46,XY partial gonadal dysgenesis: A case report and literature review

RATIONALE

Disorders/differences of sex development (DSD) include a diverse group of congenital conditions in which the development of chromosomal, gonadal, or anatomical sex is discordant. It involves several variant genes, and one of them is NR5A1. NR5A1 encodes a signal transduction regulator in the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal pathway, and pathogenic mutation in this gene is a cause of 46,XY DSD.

PATIENT CONCERNS

A 12-year-old individual raised as a girl was admitted to the hospital due to hirsutism and a deep voice that began at 11 years old. The individual exhibited testicular hypoplasia, clitoral hypertrophy, and female external genitalia.

DIAGNOSES

The patient was diagnosed 46,XY partial gonadal dysgenesis. The cytogenetics revealed a 46,XY karyotype and DNA sequencing shown a variant in NR5A1. Pelvic magnetic resonance imaging showed absence of uterus and ovaries. The abdominopelvic ultrasound revealed bilateral testicle in bilateral groin. Pathology confirmed testes dysgenesis.

INTERVENTIONS

The patient underwent bilateral orchiectomy at age 12 years and was given a feminizing hormonal treatment of 0.5 mg/day of estradiol valerate tablets.

OUTCOMES

The patient recovered well after surgery and hormonal treatment and had a regression in hirsutism and clitoromegaly.

LESSONS

46,XY DSD is a rare disease that the development of chromosomal, gonadal, or anatomical sex is discordant, when diagnosed 46,XY DSD, the identification of an NR5A1 variant should be considered.

First evidence of gonadal hybrid dysgenesis in Chagas disease vectors (Hemiptera, Triatominae): gonad atrophy prevents events of interspecific gene flow and introgression

BACKGROUND

Hybridization events between Triatoma spp. have been observed under both natural and laboratory conditions. The ability to produce hybrids can influence different aspects of the parent species, and may even result in events of introgression, speciation and extinction. Hybrid sterility is caused by unviable gametes (due to errors in chromosomal pairing [meiosis]) or by gonadal dysgenesis (GD). All of the triatomine hybrids analyzed so far have not presented GD. We describe here for the first time GD events in triatomine hybrids and highlight these taxonomic and evolutionary implications of these events.

METHODS

Reciprocal experimental crosses were performed between Triatoma longipennis and Triatoma mopan. Intercrosses were also performed between the hybrids, and backcrosses were performed between the hybrids and the parent species. In addition, morphological and cytological analyzes were performed on the atrophied gonads of the hybrids.

RESULTS

Hybrids were obtained only for the crosses T. mopan♀ × T. longipennis♂. Intercrosses and backcrosses did not result in offspring. Morphological analyses of the male gonads of the hybrids confirmed that the phenomenon that resulted in sterility of the hybrid was bilateral GD (the gonads of the hybrids were completely atrophied). Cytological analyses of the testes of the hybrids also confirmed GD, with no germ cells observed (only somatic cells, which make up the peritoneal sheath).

CONCLUSIONS

The observations made during this study allowed us to characterize, for the first time, GD in triatomines and demonstrated that gametogenesis does not occur in atrophied gonads. The characterization of GD in male hybrids resulting from the crossing of T. mopan♀ × T. longipennis♂ highlights the importance of evaluating both the morphology and the cytology of the gonads to confirm which event resulted in the sterility of the hybrid: GD (which results in no gamete production) or meiotic errors (which results in non-viable gametes).

Mini review: Breast cancer care in individuals with differences of sexual development

Disorders or differences of sexual development encompasses an important group of conditions that affects up to 1 in 5,000 live births. Many individuals living in the female gender includes Turner syndrome, congenital adrenal hyperplasia and conditions with 46XY karyotype such as gonadal dysgenesis (Swyer syndrome). Individuals are commenced on high dose oestrogen to initiate and maintain development of secondary sexual characteristics such as breasts which is paramount in them identifying in the female gender. We highlight the first case of a patient with Swyer syndrome who was treated with long term oestrogen therapy and later developed breast cancer. In individuals with gonadal dysgenesis, testicular malignancy is a recognised risk and is screened for. Prolonged exposure to exogenous and endogenous hormones can increase the risk of breast cancer however how much this risk increases in those taking high dose hormones is not documented in the literature. We aim to highlight the importance of breast cancer treatment and surgical reconstruction in this group and whether they should be considered for early breast cancer screening. CONCLUSION: It is imperative that triple assessment is undertaken in every patient with a breast lump, regardless of gender identification. Clinicians must not delay investigations in this patient group due to a misunderstanding of their condition. Those on long term hormone supplementation should be entered into the breast screening program at an earlier age with Magnetic Resonance Imaging surveillance. Careful consideration of post treatment endocrine therapy is required and under the care of the multi-disciplinary team.

Loss of function of FIGNL1, a DNA damage response gene, causes human ovarian dysgenesis

Ovarian dysgenesis (OD), an XX disorder of sex development, presents with primary amenorrhea, hypergonadotrophic hypogonadism, and infertility. In an Ashkenazi Jewish patient with OD, whole exome sequencing identified compound heterozygous frameshifts in FIGNL1, a DNA damage response (DDR) gene: c.189del and c.1519_1523del. Chromosomal breakage was significantly increased in patient cells, both spontaneously, and following mitomycin C exposure. Transfection of DYK-tagged FIGNL1 constructs in HEK293 cells showed no detectable protein in FIGNL1c.189del and truncation with reduced expression in FIGNL1c.1519_1523del (64% of wild-type [WT], P = .003). FIGNL1 forms nuclear foci increased by phleomycin treatment (20.6 ± 1.6 vs 14.8 ± 2.4, P = .02). However, mutant constructs showed reduced DYK-FIGNL1 foci formation in non-treated cells (0.8 ± 0.9 and 5.6 ± 1.5 vs 14.8 ± 2.4 in DYK-FIGNL1WT, P < .001) and no increase with phleomycin treatment. In conclusion, FIGNL1 loss of function is a newly characterized OD gene, highlighting the DDR pathway's role in ovarian development and maintenance and suggesting chromosomal breakage as an assessment tool in XX-DSD patients.

Undetectable anti-Mullerian hormone and inhibin B do not preclude the presence of germ cell tumours in 45,X/46,XY or 46,XY gonadal dysgenesis

OBJECTIVE

Individuals with 45,X/46,XY or 46,XY gonadal dysgenesis are at increased risk of germ cell malignancies. Therefore, prophylactic bilateral gonadectomy is advised in girls and considered in boys with atypical genitalia for undescended, macroscopically abnormal gonads. However, severely dysgenetic gonads may not contain germ cells rendering gonadectomy unnecessary. Therefore, we investigate if undetectable preoperative serum anti-Müllerian hormone (AMH) and inhibin B can predict the absence of germ cells, (pre)malignant or otherwise.

DESIGN, PATIENTS AND MEASUREMENTS

Individuals who had undergone bilateral gonadal biopsy and/or gonadectomy because of suspected gonadal dysgenesis in 1999-2019 were included in this retrospective study if preoperative AMH and/or inhibin B were available. Histological material was reviewed by an experienced pathologist. Haematoxylin and eosin and immunohistochemical stainings for SOX9, OCT4, TSPY and SCF (KITL) were used.

RESULTS

Thirteen males and 16 females were included, 20 with 46,XY and 9 with 45,X/46,XY DSD. Three females had dysgerminoma alongside gonadoblastoma; two gonadoblastoma, one germ cell neoplasia in situ (GCNIS) and three males had pre-GCNIS and/or pre-gonadoblastoma. Gonadoblastoma and/or dysgerminoma were present in 3/11 individuals with undetectable AMH and inhibin B, one of whom also had non-(pre)malignant germ cells. Of the other 18, in whom AMH and/or inhibin B were detectable, only one had no germ cells.

CONCLUSIONS

Undetectable serum AMH and inhibin B cannot reliably predict the absence of germ cells and germ cell tumours in individuals with 45,X/46,XY or 46,XY gonadal dysgenesis. This information should help in counselling about prophylactic gonadectomy, taking into account both the germ cell cancer risk and potential for gonadal function.

Variants in SART3 cause a spliceosomopathy characterised by failure of testis development and neuronal defects

Squamous cell carcinoma antigen recognized by T cells 3 (SART3) is an RNA-binding protein with numerous biological functions including recycling small nuclear RNAs to the spliceosome. Here, we identify recessive variants in SART3 in nine individuals presenting with intellectual disability, global developmental delay and a subset of brain anomalies, together with gonadal dysgenesis in 46,XY individuals. Knockdown of the Drosophila orthologue of SART3 reveals a conserved role in testicular and neuronal development. Human induced pluripotent stem cells carrying patient variants in SART3 show disruption to multiple signalling pathways, upregulation of spliceosome components and demonstrate aberrant gonadal and neuronal differentiation in vitro. Collectively, these findings suggest that bi-allelic SART3 variants underlie a spliceosomopathy which we tentatively propose be termed INDYGON syndrome (Intellectual disability, Neurodevelopmental defects and Developmental delay with 46,XY GONadal dysgenesis). Our findings will enable additional diagnoses and improved outcomes for individuals born with this condition.

Contribution of Clinical and Genetic Approaches for Diagnosing 209 Index Cases With 46,XY Differences of Sex Development

CONTEXT

Massively parallel sequencing (MPS) technologies have emerged as a first-tier approach for diagnosing several pediatric genetic syndromes. However, MPS has not been systematically integrated into the diagnostic workflow along with clinical/biochemical data for diagnosing 46,XY differences of sex development (DSD).

OBJECTIVE

To analyze the contribution of phenotypic classification either alone or in association with genetic evaluations, mainly MPS, for diagnosing a large cohort of 46,XY DSD patients.

DESIGN/PATIENTS

209 nonsyndromic 46,XY DSD index cases from a Brazilian DSD center were included. Patients were initially classified into 3 subgroups according to clinical and biochemical data: gonadal dysgenesis (GD), disorders of androgen secretion/action, and DSD of unknown etiology. Molecular genetic studies were performed by Sanger sequencing and/or MPS.

RESULTS

Clinical/biochemical classification into either GD or disorders of hormone secretion/action was obtained in 68.4% of the index cases. Among these, a molecular diagnosis was obtained in 36% and 96.5%, respectively. For the remainder 31.6% classified as DSD of clinically unknown etiology, a molecular diagnosis was achieved in 31.8%. Overall, the molecular diagnosis was achieved in 59.3% of the cohort. The combination of clinical/biochemical and molecular approaches diagnosed 78.9% of the patients. Clinical/biochemical classification matched with the genetic diagnosis in all except 1 case. DHX37 and NR5A1 variants were the most frequent genetic causes among patients with GD and DSD of clinical unknown etiology, respectively.

CONCLUSIONS

The combination of clinical/biochemical with genetic approaches significantly improved the diagnosis of 46,XY DSD. MPS potentially decreases the complexity of the diagnostic workup as a first-line approach for diagnosing 46,XY DSD.

Novel variant in HHAT as a cause of different sex development with partial gonadal dysgenesis associated with microcephaly, eye defects, and distal phalangeal hypoplasia of both thumbs: Case report

The palmitoylation of the Hedgehog (Hh) family of morphogens, named sonic hedgehog (SHH), desert hedgehog (DHH), and Indian hedgehog (IHH), is crucial for effective short- and long-range signaling. The hedgehog acyltransferase (HHAT) attaches the palmitate molecule to the Hh; therefore, variants in HHAT cause a broad spectrum of phenotypes. A missense HHAT novel variant c.1001T>A/p.(Met334Lys) was described in a patient first referred for a 46,XY different sexual development with partial gonadal dysgenesis but with microcephaly, eye defects, and distal phalangeal hypoplasia of both thumbs. The in silico analysis of the variant predicted an affectation of the nearest splicing site. Thus, in vitro minigene studies were carried out, which demonstrated that the variant does not affect the splicing. Subsequent protein in silico studies supported the pathogenicity of the variant, and, in conclusion, this was considered the cause of the patient's phenotype.

Causes Of Primary Amenorrhea At Tertiary Level Hospital

BACKGROUND

The objective of this study was to collect data of patients coming to us with primary amenorrhea. Finding the different causes of this problem and managing them accordingly with the help multidisciplinary team..

METHODS

In this descriptive case series, patients with primary amenorrhea coming to the Gynae A Unit, Lady Reading Hospital, Peshawar from December 2012 till September 2016 were included. Data was collected on predesigned proforma. Investigations were advised according to the protocol made by our unit. Data was analysed using SPSS version 16.

RESULTS

Total number of primary amenorrhea cases were 82. Forty-nine (59.8%) were unmarried and 33 (40.4%) were married. The mean age of the sample was 16±5.3 years. In 20 (24%) cases, there was gonadal dysgenesis. Mayer Rokistansky Kuster Hauser syndrome was found in 18 (21.9%) of cases. Constitutional and Turner syndrome in 11 (13.4%), respectively. Imperforate hymen in 7 (8.5%), vaginal septum in 5 (6.1%), swyer syndrome 2 (2.4%). Endometrial receptor deficiency in 4 (4.8%) cases. There were two cases of hypogonadotrophic hypogonadism. One case of hypothyroidism and one case of congenital adrenal hyperplasia (CAH).

CONCLUSIONS

Gonadal dysgenesis was the most common cause as compared to Mullerian duct abnormalities. Patients with endometrial receptor deficiency were more challenging. Primary amenorrhea is a distressing problem for patients as well for parents. These people are misdiagnosed and mismanaged at various occasions..

The use of testicular prostheses in boys

Lack of the testis is an important factor in psycho-sexual development of the boys, and implantation of the prosthesis plays a very essential role in the treatment of that group of patients. Currently there are no standards regarding when prosthesis should be implanted, and which access is connected with minimal rates of complications. We present our experience of primary prosthesis implantations in boys treated in our department.From 2000 to 2014, primary implantation of the testicular prosthesis was performed in 290 boys. The early and late post-operative complications and long-term therapeutic results were analyzed, considering age at the time of implantation, the time between the initial operation and implantation of the prosthesis, and the surgical approach.Best results were observed in 267 patients and bad outcome in 23 patients. Prosthesis implantation in young boys operated within the first three years of life or during the first year after primary surgery was connected with statistically fewer complications (P = .002 and P < .05, respectively). Supra-scrotal access was connected with the lowest rate of complications (P = .01).Long-term therapeutic results in boys with testicular prostheses were good in the majority of cases. Implantation of the first prosthesis should be performed early between 1 and 3 years of life in boys with lack of the testis. Implantation of a prosthesis should also be performed within 1 year after removing of testis or during orchiectomy. Supra-scrotal access should be chosen for testicular prosthesis implantation due to the best long-term results.

Congenital Juvenile Granulosa Cell Tumor of the Testis in a Fetus Showing Full 69, XXY Triploidy

Testicular juvenile granulosa cell tumor (TJGCT) occurs predominantly in infancy and may be associated with sex chromosomal abnormalities. We report a fetus aborted because of cytogenetically confirmed complete XXY triploidy. External genitalia of the fetus were female, with a short and patent vagina. The tumor presented as an abdominal multicystic mass with typical histologic and immunohistological features of JGCT. It was connected with a tubular uterus-like structure. The other gonad was an inguinally localized testis that showed histologically a Sertoli cell adenoma. Malformations typical for triploidy were also present: agenesis of the corpus callosum, stenosis of the pulmonary ostium, and hypoplasia of the lungs and adrenals. To our knowledge this is the first case of TJGCT in a triploid fetus.

Prenatal Exposures of Male Rats to the Environmental Chemicals Bisphenol A and Di(2-Ethylhexyl) Phthalate Impact the Sexual Differentiation Process

The increasing incidence of reproductive anomalies, described as testicular dysgenesis syndrome, is thought to be related to the exposure of the population to chemicals in the environment. Bisphenol A (BPA) and di(2-ethylhexyl)phthalate (DEHP), which have hormonal and antihormonal activity, have attracted public attention due to their presence in consumer products. The present study investigated the effects of BPA and DEHP on reproductive development. Timed-pregnant female rats were exposed to BPA and DEHP by gavage from gestational days 12 to 21. Results showed that prenatal exposures to test chemicals exerted variable effects on steroidogenic factor 1 and GATA binding protein 4 protein expression and increased (P < .05) sex-determining region Y-box 9 and antimüllerian hormone protein in the infantile rat testis compared with levels in the control unexposed animals. Pituitary LHβ and FSHβ subunit protein expression was increased (P < .05) in BPA- and DEHP-exposed prepubertal male rats but were decreased (P < .05) in adult animals relative to control. Exposure to both BPA and DEHP in utero inhibited (P < .05) global DNA hydroxymethylation in the adult testis in association with altered DNA methyltransferase protein expression. Together the present data suggest that altered developmental programming in the testes associated with chemical exposures are related to the disruption of sexual differentiation events and DNA methylation patterns. The chemical-induced effects impact the development of steroidogenic capacity in the adult testis.

Genital anomalies in boys and the environment

The prevalence of male reproductive disorders, such as testicular cancer and impaired semen quality, is increasing in many, albeit not all, countries. These disorders are aetiologically linked with congenital cryptorchidism and hypospadias by common factors leading to perinatal disruption of normal testis differentiation, the testicular dysgenesis syndrome (TDS). There is recent evidence that also the prevalence of genital malformations is increasing and the rapid pace of increase suggests that lifestyle factors and exposure to environmental chemicals with endocrine disrupting properties may play a role. Recent prospective studies have established links between perinatal exposure to persistent halogenated compounds and cryptorchidism, as well as between phthalates and anti-androgenic effects in newborns. Maternal alcohol consumption, mild gestational diabetes and nicotine substitutes were also identified as potential risk factors for cryptorchidism. It may be the cocktail effect of many simultaneous exposures that result in adverse effects, especially during foetal life and infancy.

aubergine mutations in Drosophila melanogaster impair P cytotype determination by telomeric P elements inserted in heterochromatin

Transposable P elements inserted in the heterochromatic Telomeric Associated Sequences on the X chromosome (1A site) of Drosophila melanogaster have a very strong capacity to elicit the P cytotype, a maternally transmitted condition which represses P element transposition and P-induced hybrid dysgenesis. This repressive capacity has previously been shown to be sensitive to mutant alleles of the gene Su(var)205, which encodes HP1 (Heterochromatin Protein 1), thus suggesting a role for chromatin structure in repression. Since an interaction between heterochromatin formation and RNA interference has been reported in various organisms, we tested the effect of mutant alleles of aubergine, a gene that has been shown to play a role in RNA interference in Drosophila, on the repressive properties of telomeric P elements. Seven out of the eight mutant alleles tested clearly impaired the repressive capacities of the two independent telomeric P insertions at 1A analyzed. P repression by P strains whose repressive capacities are not linked to the presence of P copies at 1A were previously found to be insensitive to Su(var)205; here, we show that they are also insensitive to aubergine mutations. These results strongly suggest that both RNA interference and heterochromatin structure are involved in the establishment of the P cytotype elicited by telomeric P elements, and reinforce the hypothesis that different mechanisms for repression of P elements exist which depend on the chromosomal location of the regulatory copies of P.

[Determination of the endonuclease activity encoded by retrotransposon]

Mobile element Penelope is mobilized in the course of hybrid dysgenesis in D. virilis. This element is also responsible for the activation of other unrelated families of TE occurring in the progeny of dysgenic crosses. Penelope elements have extremely variable structure and combine some properties of LINEs and LTR-containing elements. Penelope-like elements (PLEs) have been recently described in various organisms including fish species, rotifers and amoebae. Computer analysis enabled to predict the presence of reverse transcriptase domain in Penelope-encoded polyprotein as well as UvrC type endonuclease at the C-end of the element. It is noteworthy that none of the previously described retroelements was shown to contain such a nuclease. Multiple alignments revealed five conservative catalytic motifs and all conservative residues present in GIY-YIG endonuclease family within Penelope-encoded protein. Herein we have demonstrated that Penelope element isolated from D. virilis encodes functionally active endonuclease exhibiting some sequence-specificity to the sequence previously demonstrated to serve as Penelope genomic insertion site.

[The unusual mobile element Penelope and its behavior in distant Drosophila species]

The retroelement Penelope isolated from Drosophila virilis has a very unusual structure and codes for reverse transcriptase and an endonuclease belonging to the UvrC type. As shown previously, Penelope is a key element in induction of the hybrid dysgenesis syndrome described in D. virilis, which also involves mobilization of several unrelated mobile element families. Here we report a successful introduction of Penelope into the D. melanogaster genome by P element-mediated transformation. In the new host genome, Penelope is actively transcribed producing major transcript which coincides with that detected in dysgenic hybrids of D. virilis. In situ hybridization on D. melanogaster polytene chromosomes and Southern blotting revealed multiple transpositions of Penelope in the transformed D. melanogaster strains. We determined the structure of six Penelope copies inserted into D. melanogaster chromosomes. Some transformed D. melanogaster strains showed dysgenesis effects similar to those observed in hybrids from D. virilis dysgenic crosses.

Transabdominal-transperitoneal ultrasound-guided oocyte retrieval in a patient with müllerian agenesis

OBJECTIVE

To describe the approach of transabdominal-transperitoneal ultrasound-guided oocyte retrieval undertaken in a patient with müllerian agenesis and ovarian malposition who underwent a successful gestational carrier treatment cycle.

DESIGN

Case report.

SETTING

A tertiary-referral reproductive medicine unit.

PATIENT(S)

A 26-year-old patient with müllerian agenesis. Her 44-year-old mother served as the gestational carrier.

INTERVENTION(S)

Controlled ovarian hyperstimulation, transabdominal-transperitoneal ultrasound-guided oocyte retrieval, embryo transfer.

MAIN OUTCOME MEASURE(S)

Oocyte recovery rate, fertilization rate, pregnancy test.

RESULT(S)

Six oocytes were retrieved using a percutaneous transperitoneal needle puncture under ultrasound guidance. Two cleavage-stage embryos were transferred to the gestational carrier, resulting in a twin pregnancy.

CONCLUSION(S)

For various reasons, patients with müllerian agenesis may not be candidates for standard transvaginal ultrasound-guided oocyte retrieval. Although laparoscopic oocyte retrieval has been frequently used in this setting, the approach of transabdominal-transperitoneal ultrasound-guided oocyte retrieval may offer further advantages in select cases.

How valuable are model organisms for transposable element studies?

Model organisms have proved to be highly informative for many types of genetic studies involving 'conventional' genes. The results have often been successfully generalized to other closely related organisms and also, perhaps surprisingly frequently, to more distantly related organisms. Because of the wealth of previous knowledge and their availability and convenience, model organisms were often the species of choice for many of the earlier studies of transposable elements. The question arises whether the results of genetic studies of transposable elements in model organisms can be extrapolated in the same ways as those of conventional genes? A number of observations suggest that special care needs to be taken in generalizing the results from model organisms to other species. A hallmark of many transposable elements is their ability to amplify rapidly in species genomes. Rapid spread of a newly invaded element throughout a species range has also been demonstrated. The types and genomic copy numbers of transposable elements have been shown to differ greatly between some closely related species. Horizontal transfer of transposable elements appears to be more frequent than for nonmobile genes. Furthermore, the population structure of some model organisms has been subject to drastic recent changes that may have some bearing on their transposable element genomic complements. In order to initiate discussion of this question, several case studies of transposable elements in well-studied Drosophila species are presented.

Evolutionary flux of P element regulation in a Drosophila melanogaster hybrid dysgenesis cline

Clines of P-induced hybrid dysgenesis provide a means for monitoring the evolution of transposition repression over space and time. We have studied the molecular and phenotypic profiles of flies taken from a 2900 km cline along the eastern coast of Australia, which had previously been characterized over 10 years ago as having P populations in the north, Q populations at central sites and M' populations in the south. We have found that Q and M' populations of flies have increased their range within the cline at the expense of P lines. Q populations were found to be in the north of the cline and M' populations in the south. Some of the northern Q lines transmit repression through both sexes and type I deletion elements have been isolated from them. We suggest that these elements are responsible for Q type repression. The results support our model that populations made up of Q individuals with strong biparentally transmitted repression form an evolutionarily stable strategy for the repression of hybrid dysgenesis in Drosophila melanogaster.

FISH and PCR analysis of the presence of Y-chromosome sequences in a patient with Xq-isochromosome and testicular tissue

Mixed gonadal dysgenesis includes a heterogeneous group of different chromosomal, gonadal, and phenotypic abnormalities, characterized by the presence of a testis on one side and streak or an absent gonad on the other, persistence of müllerian duct structures and/or wolffian derivatives, and a variable degree of genital ambiguity. Here, we describe a patient with virilized external genitalia and phenotypic features of Turner syndrome, whose blood karyotype was 45,X/46,X,i(Xq). The presence of a unilateral dysgenetic testis was confirmed by histopathology. Using fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR)-based analysis to detect Y-specific sequences, Y-chromosome material was not detected. To date, this is the first case reported of Xq-isochromosome associated with the presence of testicular tissue.

Abnormalities of the external genitalia

This article discusses the general nuances of hypospadias, exstrophy/epispadias, and ambiguous genitalia. Embryologic considerations, etiologic factors, anatomy, associated anomalies, and timing of referrals and surgery are discussed.

[Genetic instability in the Drosophila melanogaster lozenge locus: characteristics of the lz75V locus]

Genetic properties of lz75V, an unstable allele of the lozenge locus, are described. The lz75V allele appeared in progeny of a male from a Far East natural population of Drosophila melanogaster. Mutation of this allele produces a broad spectrum of mutant derivatives with phenotypes varying from normal to extreme. The arising alleles can be stable or unstable. Some lz75V derivatives continuously preserve their spontaneous mutability in laboratory conditions, whereas other alleles of the same family show progressive stabilization at the intralocus or intrachromosome level. Instability of the lz75V-bearing X chromosome is locus-specific: only the lozenge gene mutates with high frequency, while visible mutations at other loci rarely occur. As shown previously, the lz75V allele appears to be caused by a P-element insertion. The appearance of spontaneous instability is discussed with regard to the general problem of transposition regulation in mobile elements. Different systems of hybrid dysgenesis, and, in particular, P elements are assumed to play an important role in induction of unstable mutations in nature.

Prevalence of localized rearrangements vs. transpositions among events induced by Drosophila P element transposase on a P transgene

We have studied P transposase-induced events on a P[w] transgene, P[wd1], harboring the whole white gene with a 3.44-kb direct duplication of its 5' regulatory sequences (containing the ZESTE-binding region, ZBR). We have recovered mutations leading to an increase or a decrease of zeste1 repression, generally as the consequence of modifications of number of ZBR in close physical proximity and/or jumps to other sites. We describe mutants displaying deletions of the original duplicated sequence or increases in the number of repeats from two to three or four. Internal deletions are more frequent than amplifications. Both require the integrity of P-element ends. We have also observed a high frequency of double P elements localized at the original P[wd1] insertion site. These double P elements are arranged in nonrandom configurations. We discuss the frequencies and the possible mechanisms leading to the various types of derivatives, in light of the current models for P excision and transposition. We propose that the P transposase induces mainly localized events. Some of these could result from frequent changes of template during gap-repair DNA synthesis, and/or from abortive transposition.

Diverse transposable elements are mobilized in hybrid dysgenesis in Drosophila virilis

We describe a system of hybrid dysgenesis in Drosophila virilis in which at least four unrelated transposable elements are all mobilized following a dysgenic cross. The data are largely consistent with the superposition of at least three different systems of hybrid dysgenesis, each repressing a different transposable element, which break down following the hybrid cross, possibly because they share a common pathway in the host. The data are also consistent with a mechanism in which mobilization of a single element triggers that of others, perhaps through chromosome breakage. The mobilization of multiple, unrelated elements in hybrid dysgenesis is reminiscent of McClintock's evidence [McClintock, B. (1955) Brookhaven Symp. Biol. 8, 58-74] for simultaneous mobilization of different transposable elements in maize.

[Male pseudohermaphroditism]

Male pseudohermaphroditism (MPH) is a complex variety of sexual differentiation disorders characterized by deficiency of masculinization of the internal and/or external genital organs in the presence of testicular development as the male gonad. This condition is caused by embryonic failure in the processes of male sexual development, which is a sequence of mechanisms originating from the genetic sex determination triggered by the SRY gene on the Y chromosome, followed by genital sex differentiation influenced by the fetal testis. Resulting phenotypical features of MPH vary from complete female to mostly normal but with some ambiguity in the maleness. Pubertal changes are also important factors related to etiology. Recent elucidation of detailed mechanisms of male differentiation and its derangements has been achieved in the era of molecular genetics. Classical classification of MPH, mainly based on anatomical and endocrinological findings obviously needs to subject to a complete revision. The newest version of MPH classification is reviewed and discussed in relation to etiological backgrounds of each type of the disorder. Main etiological factors are: failure of the SRY and its related genes involved in the testis determination; failure of anti-mülerian hormone (AMH) for normal involution of the female duct system; disordered production or function of androgen receptors essential for the fetal differentiation of the male genital organs; 5 alpha-reductase deficiency syndrome; defective responsiveness of the testis to gonadotropin due to Leydig cell agenesis; various types of enzyme defects involved in testicular androgen biosynthesis; fetal testicular dysgenesis syndromes occurring at various stages of embryogenesis; and other less clearly defined entities of MPH. Implications are that other types of sexual differentiation disorders than MPH, such as true hermaphroditism, gonadal dysgenesis and some other disorders that have been considered to be distinct entities, may have close linkage to MPH through dysgenetic process of gonadal development with subsequent degeneration and/or tumorigenesis. Molecular basis of these probably related disorders should be elucidated in the near future and some clues to preventive measures for these genetically determined malformations are awaited.

Germ-line expression of a functional LINE from Drosophila melanogaster: fine characterization allows for potential investigations of trans-regulators

The I factor (IF) is a functional non-viral retrotransposon, or LINE, from Drosophila melanogaster. It is mobilized in the germ-line of dysgenic SF females during I-R hybrid dysgenesis. In previous papers (Lachaume et al., Development 115: 729-735, 1992; Lachaume and Pinon, Mol. Gen. Gen. 240: 277-285, 1993) we used a transgenic fusion between the 5' part of the IF and the lacZ gene to characterize IF expression and its regulation. This I-lacZ transgenic fusion expresses beta-galactosidase activity during oogenesis. We established a Drosophila line bearing four transgenic insertions (the 4I-lacZ line) and got new insights about IF expression: (1) I-lacZ expression is proportional to the copy number of transgenes present in the genome, (2) the expression occurs just before or when meiosis begins, (3) this expression seems to be subjected to a variegation effect within the germ-line cells, (4) the transgenic activity is mainly directed toward the decondensed chromatin of nurse cells. The close relationship between I factor expression and oogenesis led us to investigate the role played by genes expressed during oogenesis on I factor expression. We present recent data indicating that mutants which interfere with oogenesis can also affect I factor expression. From this data we propose an original screen using the 41-lacZline to detect identified mutations which also affect I factor expression.

A type of incompatibility between genes and their genetic background inducing decrease in heterozygote viability approximately equal to that of homozygotes, found in a natural population of Drosophila

In the Osaka population of Drosophila melanogaster, we found an incompatibility between second chromosomes and their genetic backgrounds, where a decrease in the average viability of heterozygotes in the foreign genetic background relative to that of the native one (A'/A = 0.889) was about equal to that in non-lethal homozygotes (C'/C = 0.874). This feature is different from that of the incompatibility found in the Ishigakijima population, where little difference in average viabilities of heterozygotes between the native and foreign backgrounds was found, whereas in mean non-lethal homozygotes viabilities a large decrease was seen. This feature is supposed to be induced by the P-M hybrid dysgenesis, as strong P-transposase activity was shown in this population with the GD sterility test. Although a property similar to that of the Osaka population had been detected in the Katsunuma population, an increased frequency of the lethal-carrying chromosomes had been found in the foreign genetic background relative to the native one, and was not seen in the Osaka population.

Chronic administration of melatonin induces changes in porphyrins and in the histology of male and female hamster harderian gland: interrelation with the gonadal status

In this paper, we have investigated the influence of melatonin on the histology and porphyrin content of the Syrian hamster Harderian glands. Daily afternoon injections of 25 micrograms of melatonin to female hamsters for 12 weeks resulted in the discontinuity of estrous cyclicity, a marked decrease in the Harderian gland intraluminal area occupied by porphyrins, and in a significant rise in the number of Type II cells. A similar decrease in porphyrins was observed after 8 weeks of ovariectomy. However, if the melatonin injections were given for only 8 weeks (without inducing gonadal atrophy), no changes were observed in the area occupied by intraluminal porphyrins, suggesting that the effects of melatonin in female Syrian hamsters might be associated with the subsequent gonadal atrophy. Castration of male hamsters induced a significant increase in porphyrins and a clear drop in the number of Type II cells. These changes were totally prevented when melatonin was administered daily from the day of castration. Our results suggest that melatonin, at least in male Syrian hamsters, plays a role in Harderian metabolism, acting directly on the Harderian secretory cells or indirectly through pituitary hormones.

Evidence for retrotransposition of the I factor, a LINE element of Drosophila melanogaster

LINEs are transposable elements found in various eukaryotes such as plants, protists, insects, and mammals. Their transposition is usually difficult to study, particularly in humans, where some diseases have been shown to result from LINE insertion mutations. This is due to the fact that most copies of any particular family of elements are defective and that their transposition frequency is low. By contrast, the I factor of Drosophila melanogaster transposes at high frequency during I-R hybrid dysgenesis and is a good model for studying the LINE element superfamily. LINEs encode putative polypeptides showing similarities with viral reverse transcriptases but, unlike viral retrotransposons, they do not have terminal repeats and their ability to transpose by reverse transcription has previously only been inferred from structural analysis. Here we present direct evidence for LINE retrotransposition. Transposition of an I factor marked by an intron resulted in accurate removal of the intron.

Pregnancies following ovum donation in gonadal dysgenesis

Between February 1987 and February 1989, 13 women with primary ovarian failure due to gonadal dysgenesis were treated with embryo transfer following ovum donation in 22 cycles. Eight pregnancies were obtained (36.7% per transfer); four births of normal children, two spontaneous abortions and two other pregnancies currently ongoing (between 5 and 8 months). An association of percutaneous oestradiol, oestradiol valenate and intravaginal progesterone was used as hormone substitution and embryo transfer was only performed following assessment of the endometrium during a previous cycle. Apart from the day of embryo transfer, which was the same for all patients (the 2nd day after initiation of progesterone) various prognostic factors were analysed. These were the type of gonadal dysgenesis (45 XO, 46 XX or 46 XY), the number of embryos replaced, whether they had been frozen, whether the egg donor was anonymous and finally the influence of the hormone substitution protocol. Only the number of embryos replaced and the substitution protocol seemed to influence the implantation rate. The other parameters, and in particular the type of gonadal dysgenesis, seemed to have no effect on the results. The pregnancy rate per transfer was 30% for 45 XO (10 transfers), 25% for 46 XX (eight transfers) and 75% for 46 XY (four transfers).

Aspartylglucosaminuria in a Puerto Rican family: additional features of a panethnic disorder

We report on 3 Puerto Rican brothers with the clinical and laboratory findings of aspartylglucosaminuria (AGU). Their parents were first cousins. The affected sibs have the "cardinal" manifestations of AGU, including developmental disabilities, progressive "coarsening" of the face, and early onset of hepatosplenomegaly. Biochemical studies showed elevated levels of urinary aspartylglucosamine and very low activity of aspartylglucosaminidase(AGA) in cultured fibroblasts. With long term follow-up, previously undescribed manifestations were noted, including radiographic evidence of spondylolysis and spondylolisthesis in early childhood and development of macro-orchidism during puberty. This family shows that AGU is not limited to individuals of Finnish background, but that the gene is panethnic in distribution and that additional changes, not previously noted, may present with advancing age.

The influence of nonautonomous P elements on hybrid dysgenesis in Drosophila melanogaster

An inbred line of the M' strain Muller-5 Birmingham was studied for its abilities to affect P-M hybrid dysgenesis. This strain possesses 57 P elements, all of which are apparently defective in the production of the P transposase. In combination with transposase-producing elements, these nonautonomous elements can enhance or diminish the incidence of hybrid dysgenesis, depending on the trait that is studied. Dysgenic flies that have one or more paternally-derived chromosomes with these elements partially repress the instability of the P element insertion mutation, snw; however, such flies have elevated frequencies of another dysgenic trait, GD sterility, and also show distorted segregation ratios. An explanation is presented in which all of these phenomena are unified as manifestations of the kinetics of P element activation in the germ line. The progeny of Muller-5 Birmingham females exhibit partial repression of both snw instability and GD sterility. This repression appears to involve a factor that can be transmitted maternally through at least two generations. This mode of repression therefore conforms to the pattern of inheritance of the P cytotype, the condition that brings about nearly total repression of P element activity in some strains. Models in which this repression could arise from the nonautonomous P elements of Muller-5 Birmingham are discussed.

Hybrid dysgenesis in D. melanogaster is not a general release mechanism for DNA transpositions

Many spontaneous mutations are caused by the insertion or excision of DNA elements. Since most mutations are deleterious, evolution should favor a mechanism for genetically controlling the rate of movement of transposable elements in most, if not all, organisms. In Drosophila melanogaster a syndrome of correlated genetic changes, including mutation, chromosome breakage, and sterility, is observed in the hybrid progeny of crosses between different strains. This syndrome, which is termed hybrid dysgenesis, results from the movement of P-DNA elements. What is not clear is whether the movement of other types of transposable elements is under the same coordinated control. In this study the ability of hybrid dysgenesis to increase the rate of excision of 12 DNA elements at 16 mutant alleles and to induce insertion-bearing mutations to change to other mutant states was tested. The data show that hybrid dysgenesis caused by P-element transpositions does not act as a general stimulus for the movement of other Drosophila transposable elements.

hobo is responsible for the induction of hybrid dysgenesis by strains of Drosophila melanogaster bearing the male recombination factor 23.5MRF

The male recombination factor 23.5MRF, isolated ten years ago from a natural Greek population of Drosophila melanogaster, has been shown to induce hybrid dysgenesis when crossed to some M strains, in a fashion slightly different from that of most P strains. Furthermore, it was recently shown that 23.5MRF can also induce GD sterility when crossed to specific P strain females (e.g., Harwich, pi 2 and T-007). In these experiments, the P strains mentioned behaved like M strains in that they did not induce sterility in the reciprocal crosses involving 23.5MRF. We extended the analysis to show that 23.5MRF does not destabilize snW(M) and that a derivative with fewer full-length P elements behaves like an M strain toward the same P strains and still retains its dysgenic properties in the reciprocal crosses. We show that there is a strong correlation between the site of dysgenic chromosomal breakpoints induced by 23.5MRF and the localization of hobo elements on the second chromosome, and also that hobo elements are found associated with several 23.5MRF induced mutations. These results suggest that hobo elements are responsible for the aberrant dysgenic properties of this strain, and that they may express their dysgenic properties independent of the presence of P elements.